Retard roller

ABSTRACT

Various embodiments and methods relating to use of a retard roller opposite a driven roller are disclosed.

BACKGROUND

During picking of sheets of media from a stack, multiple sheetssometimes stick together, resulting in a multi-pick. Mechanisms forseparating the sheets that are stuck together may occupy valuable space,may be complex or may be ineffective at reducing the occurrence ofmulti-picks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a printing system according to anexample embodiment.

FIG. 2 is a schematic illustration of a media feed system of theprinting system of FIG. 1 illustrating initial picking of a sheetaccording to an example embodiment.

FIG. 3 illustrates the media, feed system of FIG. 2 during picking of asingle sheet according to an example embodiment.

FIG. 4 illustrates the media, feed system of FIG. 2 during picking ofmultiple sheets according to an example embodiment.

FIG. 5 is an enlarged view of the media feed system of Figure numeralfor according to an example embodiment.

FIG. 6 is a fragmentary perspective view of another embodiment of theprinting system of FIG. 1 according to an example embodiment.

FIG. 7 is a fragmentary perspective view of a door, retard rollers andtheir retainers of the printing system of FIG. 6 according to an exampleembodiment.

FIG. 8 is another perspective view of the retard rollers and theirretainers of FIG. 7 according to an example embodiment.

FIG. 9 is a sectional view of a retard roller of the printing system ofFIG. 6 according to an example embodiment.

FIG. 10 is an exploded view of the retard roller of FIG. 9 with portionsshown in section according to an example embodiment.

FIG. 11 is a schematic illustration of another embodiment of theprinting system of FIG. 1 according to an example embodiment.

FIG. 12 is a sectional view of a retard roller of the printing system ofFIG. 11 according to an example embodiment.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

FIG. 1 schematically illustrates media interaction system 20 includingmedia feed system 30 according to an example embodiment. As will bedescribed hereafter, media feed system 30 of media interaction system 20is a relatively low cost and less complex mechanism that reducesmulti-picking of sheets.

Media interaction system 20 includes media input 24, media output 26,media interaction device 28, media feed system 30, actuator 32 andcontroller 34. Media input 24 comprises one or more structuresconfigured for storing and positioning a stack 36 of media sheets 38waiting to be fed to media interaction device 28 by media feed system30. Media input 24 may comprise a tray, bin or other structure. In theexample illustrated, media input 24 comprises a substantially horizontalsupport surface having portion that extend opposite to portions of mediafeed system 30. In other embodiments, media input 24 may comprise aninclined support surface.

Media output 26 comprises one or more structures for storing andcontaining sheets 38 after such sheets 38 have been interacted upon bymedia interaction device 28. Media output 26 provides access to suchsheets. In one embodiment, maybe output 26 may comprise a tray, been orthe like. In yet other embodiments, media output 26 may alternatively beconfigured to redirect such interacted upon sheets 3 8 to other devicesfor further interaction.

Media interaction device 28 comprises a device configured to interactwith sheets 38. For purposes of this disclosure, the term “interact”with respect to media interaction vice 28 means a modification of sheets38 or the reading or sensing of printing or images on such sheets.Examples of such interactions include the sheets being printed upon,folded, creased, stapled or scanned. In embodiments where mediainteraction device 28 is configured to print upon sheets 38, mediainteraction device 28 may comprise a drop-on-demand ink jet printer, anelectrophotographic printer or other device is configured to form animage upon a sheet of media.

Media feed system 30 comprises an arrangement of components configuredto pick individual sheets 38 from stack 36 and to initiate the transferof such picked sheets to media interaction device 28. Media feed system30 includes friction pad 42, pick tire 44, separation surface 46, drivenroller 48, retard roller 50, feedroller 52 and idling roller 54.Friction pad 42 comprises an area configured to have a highercoefficient of friction with sheets 38 as compared to the media supportsurface of media input 24. Friction pad 42 extends along the mediasupport surface provides by media input 24 and extends substantiallyopposite to pick tire 44. Friction pad 42 assists in separating sheets38 from stack 36. In one embodiment, friction pad 42 comprises a pad ofcompressive or material such as cork. In other embodiments, friction pad42 may comprise other materials having higher coefficient of frictionwith sheets 38 as compared to media input 24. In other embodiments,friction pad 42 may be omitted.

Pick tire 44 comprises a cylindrical or substantially D-shaped rollerthat is configured to frictionally engage a topmost sheet 38 of stack 36while being rotationally driven to move the sheet in the directionindicated by arrow 60. In one embodiment, pick tire 44 is configured tobe selectively moved into engagement or moved out of engagement with thetop most sheet 38. In other embodiments, pick tire 44 may be cylindricalor may have other shapes. Although system 30 is illustrated as includinga single pick tire 44, in other embodiments, system 30 may includeadditional pick tire 44 space along a top surface of the top of sheet38.

Separation surface 46 comprises a vertically inclined surface configuredto abut leading edges 62 of sheets 38 that are driven by pick tire 44prior to such sheets 38 being engaged in driven by driven roller 48. Inone embodiment, separation surface 46 has a coefficient of friction withsuch leading edges 62 such that frictional forces exerted by separationsurface 46 upon the topmost sheet 38 are less than the driving foursupply by pick tire 44 to the topmost sheet and such that frictionalforces applied by separation surface 46 to underlying sheets 38 orgreater than the driving force apply to such underlying sheets by picktire 44 as a result of friction between the topmost sheet 38 and suchunderlying sheets. In such an embodiment, separation surface 46 furtherassists in separating the top most sheet 38 of stack 36 from underlyingsheets 38 to reduce occurrences of a multi-pick. As indicated by arrow66, sheets driven by pick tire 44 are moved up a long separation surface46 to a downwardly facing at 68 formed by driven roller 48 and retardroller 50.

Driven roller 48 and retard roller 50 cooperate to further move thetopmost sheet 38 being driven by pick tire 44 towards media interactiondevice 28. At the same time, driven roller 48 and retard roller 50increase the effectiveness of system 30 at reducing the occurrence ofmulti-picks. Driven roller 48 comprises a roller rotationally driven byactuator 32 to drive sheets 38 along a media path. Although system 30 isillustrated as including a single driven roller 48, in otherembodiments, system 30 may include multiple spaced driven rollers 48.

Retard roller 50 comprises a roller rotationally supported opposite todriven roller 48. Retard roller 50 is configured to be urged intocontact with driven roller 48 in the absence of a sheet 38 betweenroller 48 and roller 50. Retard roller 50 is configured to frictionallyengage or grip a sheet 3P, in contact with roller 50. Retard roller 50is resiliently biased against rotation. In one embodiment, the biasapplied to retard roller 50 is such that torque transmitted to retardroller 50 during rotation of driven roller 48, when driven roller 48 isin direct contact with retard roller 50 or when a single sheet 38 ispositioned between and in mutual contact with both driven roller 48 andretard roller 50, is sufficient to overcome the bias. As a result,rotation of driven roller 48 in a counterclockwise direction as seen inFIG. 1 also results in rotation of retard roller 50 in a clockwisedirection as seen in FIG. 1. At the same time, the bias applied toretard roller 50 is such that when a multi-pick is occurring (when twoor more sheets 38 are positioned between driven roller 48 and retardroller 50), the forced transmitted from driven roller 48 to retardroller 50 through the two or more intervening sheets 38 is insufficientto overcome the bias applied to retard roller 50. The torque applied toretard roller 50 during a multi-pick is much less than the torqueapplied to retard roller when a single sheet 38 is being picked becauseof the multiple intervening sheets 38 that transmit only a small portionof the friction force from driven roller 48 due to their relativesmaller media to media coefficients of friction compared with rubberroller to media coefficients of friction. In one embodiment, retardroller 50 is resiliently biased against rotation by one or more torsionsprings (not shown).

Because retard roller 50 is resiliently biased against rotation, retardroller 50 applies a drag to the second sheet that is being multiplepicked and that is not in contact with driven roller 48. Because retardroller 50 is in contact with controller 34 and the absence of anyintervening sheets 38 and because such bias is overcome by the torqueapplied to driven roller 50 by driven roller 48, retard roller 50 istorsionally loaded or wound up. Upon being torsionally loaded, retardroller 50 further configured to further rotate or slip (such as with aclutch or other mechanism) without further torsional loading. As aresult, single sheets 38 may be driven by driven roller 48 onward alonga media path towards media interaction device 28. However, during amulti-pick, the forces exerted against retard roller 50 are insufficientto overcome the bias such that retard roller 50 torsionally unloadswhile in contact with the second sheet (i.e., the sheet that is not incontact with driven roller 48) to drive or kick the second sheet awayfrom nip 68 and back towards separation surface 46. Because the leadingedge 62 of the second sheet is propelled away from nip 68 and backtowards separation surface 46 and media input 24, the occurrence ofmulti-picks may be reduced.

Feedroller 52 and idling roller 54 cooperate to further move pickedsheets 38 along a media path at least partially defined by roller 52 and54. Feedroller 52 is operably coupled to actuator 32 and is rotationallydriven by actuator 32. Idling roller 54 extends opposite to feedroller52 and is urged towards and against roller 52 to form a nip 72. Idlingroller 54 is configured to freely rotate without imposing substantialdrag upon a sheet 38 being driven by feedroller 52. In otherembodiments, the roller 52 and idling roller 54 may be omitted.

Actuator 32 comprises a device configured to rotationally drive picktire 44, driven roller 48 and feedroller 52. In one embodiment, actuator32 may comprise a motor operably coupled to pick tire 44, driven roller48 and feedroller 52 by a drive train or transmission 55 (schematicallyshown). Although actuator 32 is illustrated as driving each of pick tire44, driven roller 48 and feedroller 52, in other embodiments, separateactuators may alternatively be provided.

Controller 34 comprises one or more processing units configured togenerate control signals directing the operation of at least actuator 32and of media interaction device 28. For purposes of this application,the term “processing unit” shall mean a presently developed or futuredeveloped processing unit that executes sequences of instructionscontained in a memory. Execution of the sequences of instructions causesthe processing unit to perform steps such as generating control signals.The instructions may be loaded in a random access memory (RAM) forexecution by the processing unit from a read only memory (ROM), a massstorage device, or some other persistent storage. In other embodiments,hard wired circuitry may be used in place of or in combination withsoftware instructions to implement the functions described. For example,controller 34 may be embodied as part of one or moreapplication-specific integrated circuits (ASICs). Unless otherwisespecifically noted, the controller is not limited to any specificcombination of hardware circuitry and software, or to any particularsource for the instructions executed by the processing unit.

FIGS. 2-5 schematically illustrate operation of media feed system 30.FIG. 2 schematically illustrates the initiation of picking of one ormore sheets 38. As shown by FIG. 2, pick tire 44 is rotationally drivenin the direction indicated by arrow 76 to drive the top most sheet 38against and upwards along separation surface 46. Prior to engagementwith the top most sheet 38, driven roller 48 is also rotationally drivenin a counterclockwise direction as indicated by arrow 78 while inengagement with retard roller 50. As a result, retard roller 50 is alsorotationally driven in a clockwise direction as indicated by arrow 80.During such rotation, retard roller 50 is torsionally loaded or wound upuntil retard roller 50 begins to rotationally slip with respect to aclutch or other mechanism.

FIG. 3 schematically illustrates a first scenario in which a single topmost sheet 38 is picked by pick tire 44 and is driven between nip 68.Because a single sheet 38 is in simultaneous contact with both drivenroller 48 and retard roller 50, sufficient torque is transmitted fromdriven roller 48 to retard roller 50 by the intervening sheets 38 tocontinue to drive retard roller 50 against its torsional bias such thatretard roller 50 continues to rotate in the clockwise direction asindicated by arrow 80. The single sheet is subsequently transferred to anip 72 formed between feedroller 52, driven in a counterclockwisedirection as indicated by arrow 82, and idling roller 54.

FIGS. 4 and 5 illustrate a second alternative scenario in which amulti-pick is taking place. As a result, both a top most sheet 38 and anunderlying sheet 38 extend into nip 68 and between driven roller 48 andretard roller 50. Because the two sheets 38 between rollers 48 and 50have lower coefficients of friction with respect to one another ascompared to the coefficient of friction of such sheets with rollers 48and 50, a lesser amount of torque is transmitted from driven roller 48across the intervening sheets 38 to retard roller 50. This lesser forceis insufficient to overcome the bias of retard roller 50. As a result,retard roller 50 torsionally unloads or unwinds by rotating in acounterclockwise direction as indicated by arrow 84. Consequently, asseen in FIG. 5 and as indicated by arrow 86, retard roller 50 drives orpropels the leading edge 62 of the underlying sheet 38 in contact withretard roller 50 back towards separation surface 46 (shown in FIG. 4)and out of nip 68. Meanwhile, driven roller 48 continues to drive thetop most sheet 38 along the media path as indicated by arrow 88. Oncethe underlying sheet 38 has been driven out of nip 68 and retard roller50 has moved into contact with the top most sheet 38, a greater amountof torque is once again transmitted from driven roller 48 to retardroller 50 through the single intervening sheet 38. This larger amount oftorque is once again sufficient to overcome the bias of retard roller 50just to rotate retard roller 50 and a clockwise direction and totorsionally load retard roller 50 once again as described above withrespect to FIG. 3.

Overall, media feed system 30 provides a relatively low-cost and lesscomplex system for effectively separating sheets of a multi-pick.Because system 30 includes an inclined separation surface 46 inconjunction with retard roller 50, separation of sheets is enhanced. Forexample, underlying sheets driven out of nip 68 by retard roller 50during a first pick that still underlie another top most sheet 38 duringa subsequent pick may once again have to overcome the separation forceprovided by separation surface 46 prior to even reaching nip 68 during asubsequent pick. In addition, because nip 68 opens or faces in asubstantially downward or declined direction, retard roller 50additionally uses the assistance of gravity in expelling the underlyingmulti-pick sheet from nip 68. As a result, the multi-picked underlyingsheet 38 may be driven a farther distance from nip 68 reducing thelikelihood of a subsequent multi-pick with the same sheet.

FIG. 6 illustrates media interaction system 120, another embodiment ofmedia interaction system 20. Media interaction system 120 is similar tomedia interaction system 20 in that media interaction system 120includes media feed system 130, a particular example of media feedsystem 30. In addition to media feed system 130, media interactionsystem 20 includes media input 24, housing 125, a portion of which isshown in FIG. 6, media output 26 (schematically shown in FIG. 1), mediainteraction device 28, actuator 32 and controller 34, each of which isschematically shown and described with respect to FIG. 1.

Housing 125 at least partially encloses remaining components of mediainteraction 120. As shown by FIG. 6, housing 125 includes an exteriorwall 126 in which is disposed a removable door 127. Door 127 isconfigured to be removed from wall 126 to provide access to the mediafeed path adjacent to media feed system 130. Removal of door 127facilitates clearing of media jams or other issues. In one embodiment,door 127 is fastened to wall 126, wherein removal of the fasteners fromits door 127 to be withdrawn. In another embodiment, door 127 may bepivoted between an open state and a closed state. As will be describedin more detail hereafter, door 127 carries portions of media feed system130, and enhancing compactness of media interaction system 120.

Media feed system 130 includes friction pad 142, pick tires 144,separation surfaces 146 (one of which is shown), driven roller 148,retard roller retainers 149, retard rollers 150, feedroller 52 (shown inFIG. 1) and idling roller 54 (shown in FIG. 1). Feedroller 52 and idlingroller 54 are omitted from FIG. 6 for purposes of illustrating retardroller 50. Friction pad 142 is similar to friction pad 42 of system 30shown in FIG. 1. Friction pad 142 comprises an area configured to have ahigher coefficient of friction with sheets 38 (shown in FIG. 1) ascompared to the media support surface of media input 124. Friction pad142 extends along the media support surface provides by media input 124and extends substantially opposite to pick tires 144. Friction pad 142assists in separating sheets 38 from stack 36 (shown in FIG. 1). In oneembodiment, friction pad 142 comprises a pad of compressive or materialsuch as cork. In other embodiments, friction pad 142 may comprise othermaterials having higher coefficient of friction with sheets 38 ascompared to media input 124. In other embodiments, friction pad 142 maybe omitted.

Pick tires 144 comprises cylindrical or substantially D-shaped rollersthat are configured to frictionally engage a top most sheet 38 of stack36 while being rotationally driven to move the sheet towards separationsurface 146. In the embodiment illustrated, pick tires 144 are supportedby an arm 153 that is pivotally supported by housing 125 and may bepivoted by an actuator (not shown) to selectively move tires 144 intoengagement or out of engagement with the top most sheet 38. Althoughsystem 130 is illustrated as including a pair of pick tires 144, inother embodiments, system 130 may include greater or fewer pick tires 44spaced along a top surface of the top of sheet 38.

Separation surface 146 comprises a vertically inclined surfaceconfigured to abut leading edges of sheets 38 that are driven by picktires 144 prior to such sheets 38 being engaged in driven by drivenroller 48. In one embodiment, separation surface 146 has a coefficientof friction with such leading edges 62 such that frictional forcesexerted by separation surface 46 upon the topmost sheet 38 are less thanthe driving force supplied by pick tire 44 to the topmost sheet and suchthat frictional forces applied by separation surface 146 to underlyingsheets 38 are greater than the driving force apply to such underlyingsheets by pick tires 144 as a result of friction between the topmostsheet 38 and such underlying sheets. In such an embodiment, separationsurface 146 further assists in separating the top most sheet 38 of stack36 from underlying sheets 38 to reduce occurrences of a multi-pick.According to one embodiment, separation surface 146 includes a multitudeof teeth configured to resist movement of another line multi-pick sheet.In other embodiments, separation surface146 may have otherconfigurations.

Driven roller 148 comprises a plurality of rollers supported by a shaftopposite to retard rollers 150. Driven roller 48 is configured to berotationally driven by actuator 32 (shown in FIG. 1) to drive and turn asheet of media further along a media feed path. In one embodiment,driven roller 48 includes four spaced rollers, each roller positionedopposite to the corresponding four retard rollers 150. In otherembodiments, driven roller 48 may comprise a single roller, againstwhich each of retard rollers 150 are urged.

Retard roller retainers 149 pivotally support retard rollers 150 withrespect to driven roller 148 and resiliently bias each of retard rollers150 towards driven roller 148. FIGS. 6 and 7 illustrate retainers 149 inmore detail. As shown by FIGS. 6 and 7, retainers 149 each include anarm 157 and a resilient bias 159. As shown by FIG. 6, each support armsupports a retard roller 150 and is pivotally connected to door 127 atanother end. In the example illustrated, each arm 157 includes anopening 161 rotationally receiving a pin, shaft or axle 163 projectingfrom door 127. In the particular example illustrated, each arm 157 is atleast partially received within a corresponding cavity 165 provided bydoor 127. As a result, arms 157 do not substantially increase the volumeof media interaction system 120.

Biases 159 comprise spring mechanisms configured to resiliently biasarms 157 and retard rollers 150 towards driven roller 148. In theparticular example illustrated, biases 159 comprise compression springscaptured between arms 157 and door 127. In other embodiments, biases 159may comprise other spring mechanism such as torsion springs, tensionsprings or leaf springs arranged to cooperate between arms 157 and door127 to resiliently bias arms 157 and rollers 150 towards driven roller148. Because retard rollers or 150 are supported and carried by door127, retard rollers 150 may be mounted in the door 127 in place ofidling rollers, reducing an extent to which an existing printing systemarchitecture or housing would be modified to accommodate retard rollers150. In addition, the provision of retard rollers 150 does not addsignificant cost, space or complexity to media interaction system 120.

Retard rollers 150 cooperate with driven roller 148 to reducemulti-picks. Each retard roller 150 comprises a roller rotationallysupported opposite to driven roller 148 by a corresponding support arm157. Retard rollers 150 are configured to frictionally engage or grip asheet 38 in contact with roller 50. Retard rollers 50 are resilientlybiased against rotation. In one embodiment, the bias applied to retardrollers 50 is such that torque transmitted to retard rollers 50 duringrotation of driven roller 148, when driven roller 148 is in directcontact with retard roller 150 or when a single sheet 38 is positionedbetween any mutual contact with both driven roller 148 and retardrollers 50, is sufficient to overcome the bias. As a result, rotation ofdriven roller 148 in a counterclockwise direction as seen in FIG. 1 alsoresults in rotation of retard rollers 150 in a clockwise direction asseen in FIG. 1. At the same time, the bias applied to retard rollers 150is such that when a multi-pick is occurring (when two or more sheets 38are positioned between driven roller 148 and retard rollers 150), theforced transmitted from driven roller 148 to retard rollers 150 throughthe two or more intervening sheets 38 is insufficient to overcome thebias applied to retard roller 150. The torque applied to retard roller150 during a multi-pick is less than the torque applied to retard rollerwhen a single sheet 38 is being picked because of the multipleintervening sheets 38 that transmit only as portion of the force fromdriven roller 48 due to their relative lower coefficient of friction. Inone embodiment, each of retard rollers 150 is resiliently biased againstrotation by one or more torsion springs (not shown).

Because retard rollers 150 are resiliently biased against rotation,retard rollers 150 apply a drag to the second sheet that is being pickedand that is not in contact with driven roller 148. Because retard roller150 are in contact with roller 148 in the absence of any interveningsheets 38 and because such bias is overcome by the torque applied toretard rollers 150 by driven roller 148, retard rollers 150 aretorsionally loaded or wound up. Upon being torsionally loaded to apredetermined amount, retard rollers 150 are further configured tofurther rotate or slip (such as with a clutch or other mechanism)without further torsional loading. As a result, single sheets 38 may bedriven by driven roller 148 onward along a media path towards mediainteraction device 28. However, during a multi-pick, the forces exertedagainst retard roller 50 are insufficient to overcome the bias such thatretard rollers 150 torsionally unload or unwind while in contact withthe second sheet (i.e., the sheet that is not in contact with drivenroller 148) to drive or kick the second sheet away from nip 168 and backtowards separation surface 146. Because the leading edge 62 of thesecond sheet is propelled away from nip 168 and back towards separationsurface 146 and media input 24, the occurrence of multi-picks may bereduced.

FIGS. 9 and 10 illustrate one of retard rollers 150 in detail. Retardroller 150 includes shaft 200, interior clutch member 204, clutch spring206, hub 208, tire 210 and spring 212. Shaft 200 extends through clutchmember 204 and hub 208 and has ends secured to arm 157 (shown in FIG.6). In the particular example illustrated, shaft 200 has at least onenoncircular end 214 received within arm 157 (as shown in FIGS. 7 and 8)to inhibit rotation of shaft 200. Shaft 200 rotationally supports clutchmember 204 and hub 208 about axis 218. In other embodiments, shaft 200may be connected to arm 157 in other fashions such that shaft 200 issecured against rotation.

Interior clutch member 204 comprises a structure rotationally positionedabout shaft 200 within hub 208. As shown by FIG. 10, member 204 includesa key 220 axially projecting on one end of member 204. As will bedescribed hereafter, key 220 cooperates with hub 208 to limit an extentto which hub 208 may rotate with respect to member 204 without alsorotating member 204 so as to provide a preset limit to which spring 212may be torsionally loaded to potentially extend the useful life ofspring 212. Although illustrated as a tab, key 220 may have otherconfigurations.

Clutch spring 206 comprises a torsion spring encircling shaft 200 andhaving an end 226 connected to clutch member 204 and the other end isfree. Spring 206, when in a relaxed state, has an inner diameter lessthan or equal to an outer diameter of shaft 200. When in a relaxedstate, spring 206 constricts about shaft 200 such that friction betweenspring 206 and shaft 200 inhibit relative rotation of spring 206 andshaft 200 about axis 218. When in a relaxed state, spring 206 alsorestricts rotation of clutch member 204 about axis 218. Spring 206 isfurther configured such that transmission of a sufficient torque toclutch member 204 and to spring 206 results in unwinding or expansion ofspring 206 (increase its inner diameter), permitting spring 206 andclutch member 204 to rotate relative to shaft 200 with certain dragtorque. In the particular example illustrated, spring 206 is providedwith a spring constant greater than the spring constant of spring 212,spring 212 may be wound or unwound with respect to its relaxed statewith a force less than a force that would wind or unwind spring 206.

Hub 208 comprises a structure rotationally supported about axis 218 andconfigured to rigidify and support tire 210. Hub 208 further includes aninterior cavity 224 receiving clutch member 204 and spring 212,enhancing compactness of retard roller 150. As shown by FIG. 10, hub 208includes a pair of shoulders or steps 228 separated by an intermediatecircumferential gap 230. Gap 230 receives key 220. Steps 228 areconfigured to abut key 220 so as to limit rotation of key 220 past suchsteps 228. Steps 228 cooperate with key 220 to limit the extent to whichhub 208 and tire 210 may be additionally rotated about axis 218 relativeto clutch member 204 during torsional loading of spring 212. Once clutchmember 204 begins to rotate with hub 208 upon engagement of key 220 andone of the steps 228, torsional loading of spring 212 is stopped. As aresult, steps 228 provide a preset limit to which spring 212 may betorsionally loaded, providing greater control over the operation ofretard roller 150.

In one embodiment, steps 228 are angularly spaced from one another byabout 141 degrees which will give 102 degree of relative rotationbetween clutch member 204 and hub 208 because of the width of key 220.In other embodiments, the spacing may be varied depending upon specificcharacteristics of spring 212. In still other embodiments, therelationship between steps 228 and key 220 may be reversed. Inparticular, hub 208 may alternatively include key 220 while clutchmember 204 alternatively includes steps 228 and gap 230.

Tire 210 comprises one or more layers of one or more materialsconfigured to frictionally engage a sheet of media. Tire 210 issupported about axis 218 by hub 208. In one embodiment, tire 210comprises a layer of a resiliently compressible material, such asrubber. In other embodiments, tire 210 may comprise other compressiblematerials. In some embodiments, tire 210 may additionally includesurface texturing, ridges, grooves, dimples or the like to enhance acoefficient of friction between an outer surface of tire 210 and a sheetof media being contacted and gripped by tire 210. In yet otherembodiments, tire 210 may be omitted, wherein hub and 208 is configuredto frictionally engage and contact a sheet of media.

Spring 212 comprises a torsion spring extending about shaft 200 withincavity 224. Spring 212 has a first end 232 connected to hub 208 and asecond end 234 connected to clutch member 204. In the particularembodiment illustrated, spring 212 is configured to be wound up whenbeing rotated in a first direction during torsional loading of spring212, whereas spring 206 is configured to be unwound when rotated in thesame first direction. As a result, cavity 224 may be reduced in size,decreasing the size of retard roller 150. In other embodiments, spring212 may alternatively be unwound during torsional loading. In theparticular embodiment illustrated, spring 212 is configured so as toexperience minimal or no frictional resistance from either shaft 200 orhub 208. Spring 212 is provided with a spring constant less than aspring constant of spring 206. As a result, spring 212 may betorsionally loaded while clutch member 204 is held against rotation byspring 206.

In operation, in the absence of a sheet between retard roller 150 anddriven roller 148 such that driven roller 148 is in engagement with tire210 or wherein a single sheet is in concurrent contact with both drivenroller 148 and tire 210 retard roller 150 is driven by torque providedby driven roller 148. During such rotation, hub 208 rotate about axis218 relative to clutch member 204 which is held against rotation byclutch spring 206. At the same time, rotation of hub 208 further windsspring 212 to torsionally load spring 212. Once step 228 is rotated intoabutment with key 220, hub 208 the longer rotates relative to clutchmember 204 such that torsional loading of spring 212 is stopped.Thereafter, rotation of hub 208 transmits torque to clutch member 204 toa sufficient extent such that clutch member 204 overcomes the resistanceprovided by clutch spring 206 to unwind clutch spring 206. Unwinding ofclutch spring 206 decreases frictional engagement between clutch spring206 and shaft 200, permitting clutch member 204 and a remainder ofretard roller or 152 more freely rotate about shaft 200 and axis 218.

When a multi-pick is occurring such that two or more sheets arepositioned between driven roller 148 and retard roller 150, torquetransmitted to retard roller 150 is dependent upon a coefficient offriction between each of the multiple intervening sheets. As a result,torque received by retard roller 150 from driven roller 148 issubstantially reduced. Spring 212 is configured such that the forcetransmitted to retard roller 150 is less than the counter rotationalforce provided by spring 212. As a result, spring 212 torsionallyunloads to hub 208 and tire 210 in a direction so as to drive the sheetin contact with tire 210 in a backwards direction towards separationsurface 146 (shown in FIG. 6) and out of the nip between driven roller148 and retard roller 150.

FIG. 11 illustrates portions of media interaction system 320, anotherembodiment of printing system 20. Media interaction system 320 issimilar to printing system 20 except that media interaction system 320includes retard roller 350 in lieu of retard roller 50 and additionallyincludes brake 351. Those remaining elements of media interaction system320 which correspond to elements of printing system 20 are numberedsimilarly.

Retard roller 350 comprises one or more rollers resiliently biasedagainst rotation. FIG. 12 illustrates the retard roller 350 in detail.As shown by FIG. 12, retard roller 350 is similar to retard roller 150except that retard roller 350 omits clutch spring 206 and includes shaft400 and key support 404 in lieu of shaft 200 and clutch member 204,respectively. Those remaining elements of retard roller 350 whichcorrespond to end are substantially similar to elements of retard roller150 are numbered similarly.

Shaft 400 comprises an elongate shaft extending through hub 208 andconfigured to rotationally support hub 208. Shaft 400 is rotationallysupported for rotation about axis 418. One end of shaft 400 is operablycoupled to brake 351.

Key support 404 comprises a structure connected to shaft 400 so as torotate with shaft 400. In one embodiment, key support 404 may befastened, bonded, welded or otherwise affixed to shaft 400. In otherembodiments, support 404 may be integrally formed as a single unitarybody with shaft 400. Key support 404 includes key 220 shown anddescribed above with respect to FIG. 8. Key 220 of key support 404functions identical to key 220 of clutch member 204. In particular, key220 cooperates with steps 228 and 230 (shown in FIG. 8) of hub 208 tolimit the extent to which spring 212 is loaded.

Brake 351 comprises an adjustable and controllable braking mechanismoperably coupled to shaft 400. Brake 351 brakes or retards rotation ofshaft 400. Brake 351 applies an adjustable braking force to shaft 400based upon control signals received from controller 34 (shown in FIG.9). According to one embodiment, controller 34 generates control signalssuch that brake 351 brakes rotation of shaft 400 such that shaft 400does not rotate or rotates slower as compared to rotation of hub 208when retard roller 350 is being driven by driven roller 48 until key 220engages one of steps 228 (shown in FIG. 10). Brake 351 is controlledsuch that further transmission of torque to shaft through tire 210, hub208 and key support 404 is sufficient to overcome the braking resistanceprovided by brake 351 when driven roller 48 is in direct contact withtire 210 or when a single sheet is between driven roller 48 and tire210.

In one embodiment, media interaction system 320 additionally includes asensor 421 operably coupled to brake 351 or shaft 400 to detect whenshaft 400 starts to rotate. In response to receiving signals indicatingthat shaft 400 has begun to rotate, controller 34 may be additionallyconfigured to generate control signals decreasing the braking forcesupplied by brake 351 at an enhanced rate to quickly reduce the amountof braking resistance provided by brake 351. As a result, driven roller48 experiences a controlled and substantially smaller resistance,reducing an amount of torque used to drive driven roller 48. In such anembodiment, controller 34 may additionally be configured to generatecontrol signals directing brake 351 to increase the braking resistanceapplied by brake 351 to shaft 400 upon receiving signals from one ormore sensors (not shown) indicating that a sheet has left the nipbetween driven roller 48 and retard roller 350. In other embodiments,sensor 421 may be omitted.

According to one embodiment, brake 351 may comprise a magnetic brake. Inother embodiments, brake 351 may comprise other brakes which provide anadjustable or controllable braking force in response to control signalsfrom controller 34.

Although the present disclosure has been described with reference toexample embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the claimed subject matter. For example, although differentexample embodiments may have been described as including one or morefeatures providing one or more benefits, it is contemplated that thedescribed features may be interchanged with one another or alternativelybe combined with one another in the described example embodiments or inother alternative embodiments. Because the technology of the presentdisclosure is relatively complex, not all changes in the technology areforeseeable. The present disclosure described with reference to theexample embodiments and set forth in the following claims is manifestlyintended to be as broad as possible. For example, unless specificallyotherwise noted, the claims reciting a single particular element alsoencompass a plurality of such particular elements.

1. An apparatus for comprising: a media support surface configured tosupport a stack of sheets; a pick tire opposite the support surface; aninclined separation surface proximate the support surface and configuredto engage in edge of a sheet driven by the pick tire; a driven rollerconfigured to drive the sheet after the sheet has engaged the separationsurface; and a retard roller rotationally supported opposite the drivenroller, the retard roller being resiliently biased against rotation. 2.The apparatus of claim 1 wherein the driven roller end of the retardroller form a downwardly facing nip.
 3. The apparatus of claim 1 furthercomprising a removable housing door carrying the retard roller.
 4. Theapparatus of claim 1 further comprising a brake coupled to the retardroller to adjust drag of the retard roller.
 5. The apparatus of claim 1,wherein the retard roller comprises: a tire; a shaft extending throughthe tire and fixed against rotation; an inner member rotationallysupported within the tire; a first spring having a first end coupled tothe tire and a second and coupled to the inner member; and a secondspring extending about the shaft and having an end coupled to themember, wherein the tire and the inner member are configured tocooperatively engage one another such that rotation of the tire relativeto the member is less than 360 degrees.
 6. The apparatus of claim 5,wherein one of the tire and the inner member includes spaced steps andwherein the other of the tire and the inner member includes a keybetween the spaced steps.
 7. The apparatus of claim 6, wherein thesecond spring is configured to frictionally retain the inner memberagainst rotation until the key is in an engagement with one of thespaced steps.
 8. The apparatus of claim 5, wherein the first spring isconfigured to wind up as the second spring unwinds.
 9. The apparatus ofclaim 1 further comprising a printing device configured to print uponsheets picked by the pick tire.
 10. The apparatus of claim 1, whereinthe media support surface is substantially horizontal.
 11. An apparatuscomprising: a media support surface configured to support a stack ofsheets; a pick tire opposite the support surface; a driven rollerconfigured to drive the sheet a from the pick tire; a retard rollerrotationly supported opposite the driven roller, the retard roller beingresiliently biased against rotation; and a removable door carrying theretard roller.
 12. The apparatus of claim 11 further comprising ininclined separation surface between the pick tire and the driven roller.13. The apparatus of claim 11, wherein the retard roller comprises: atire; a shaft extending through the tire and fixed against rotation; aninner member rotationally supported within the tire; a first springhaving a first end coupled to the tire and a second end coupled to theinner member; and a second spring extending about the shaft and havingan end coupled to the member, wherein the tire and the inner member areconfigured to cooperatively engage one another such that rotation of thetire relative to the member is less than 360 degrees.
 14. The apparatusof claim 13, wherein one of the tire and the inner member includesspaced steps and wherein the other of the tire and the inner memberincludes a key between the spaced steps
 15. The apparatus of claim 14,wherein the second spring is configured to frictionally retain the innermember against rotation until the key is in an engagement with one ofthe spaced steps
 16. The apparatus of claim 13, wherein the first springis configured to wind up as the second spring unwinds
 17. A methodcomprising: torsionally loading a first spring coupled to a retardroller to a predetermined torque with a driven roller opposite theretard roller; torsionally loading a second spring to reduce frictionbetween the retard roller and a support shaft when a first sheet is incontact with the driven roller and the retard roller; and torsionallyunloading the first spring when a second sheet is in contact with theretard roller while the first sheet is in contact with the driven rollerto drive the second sheet away from the driven roller.
 18. The method ofclaim 17 further comprising picking the first sheet from a stack andmoving the first sheet against a vertical separation surface prior tothe first sheet engaging the driven roller.
 19. The method of claim 17further comprising accessing the driven roller by opening a doorcarrying the retard roller.
 20. The method of claim 17, wherein theretard roller comprises: a tire; a shaft extending through the tire andfixed against rotation; an inner member rotationally supported withinthe tire; a first spring having a first end coupled to the tire and asecond and coupled to the inner member; and a second spring extendingabout the shaft and having an end coupled to the member, wherein thetire and the inner member are configured to cooperatively engage oneanother such that rotation of the tire relative to the member is lessthan 360 degrees.